Expression ratios of the Bcl-2 family proteins and disease activity in multiple sclerosis

There is emerging evidence that failure of apoptosis (programmed cell death) of potentially pathogenic T lymphocytes may be involved in the pathogenesis of multiple sclerosis (MS). The commitment of T lymphocytes to die is partly regulated by the Bcl-2 family proteins, which act as a checkpoint upstream of mitochondrial dysfunction. These proteins include the death antagonists Bcl-2 and Bcl-X(L), and death agonists Bax and Bad. Recent studies suggest that altered expression of Bcl-2 family proteins in T lymphocytes is involved in promoting cellular resistance to apoptosis in patients with MS. However, the relationship between these alterations in Bcl-2 proteins expression and clinical disease activity has not yet been evaluated. In this study, we analyzed the expression ratios of pro- to anti-apoptosis Bcl-2 family proteins in patients with clinically active MS and compared results to corresponding ratios in patients with stable MS and relevant control groups. We observed a significant reduction in the expression ratios of pro- to anti-apoptosis Bcl-2 members in peripheral lymphocytes from patients with active MS when compared to corresponding ratios in patients with stable MS or other controls. This imbalance in the expression ratios of pro- and anti-apoptosis proteins was functionally active in reducing cellular susceptibility to apoptosis in active MS. It also correlated with clinical features of disease activity, such as the number of gadolinium-enhancing MRI lesions and clinical relapses. Our findings indicate that dysregulated expression of Bcl-2 family proteins in peripheral lymphocytes is a feature of clinically active multiple sclerosis.